<?php 

header("Content-Type: text/html; charset=UTF-8");

// $num = 123;

// var_dump($num);

// $num = "学并思";

// var_dump($num);


//传值
// $num = 123;//位置

// $num1 = &$num;

// $num1 = '学并思';

// var_dump($num,$num1);



// $a = 'hello'; //普通变量


// $$a = 'world'; //可变变量

// echo "$a ${$a}";//输出：hello world
// echo "$a $hello";//输出：hello world

$num = 1232;
// var_dump(isset($num));

unset($num);
var_dump($num)
 ?>

 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
 <html lang="en">
 <head>
 	<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
 	<title>Document</title>
 </head>
 <body>
 	<a href="./var.php?page=121"></a>
 	<a href="./var.php?page=dfdfd"></a>
 </body>
 </html>